Vehicle security system

摘要

An anti-theft system is disclosed which includes a fuel cut-off valve (12) that is controlled in response to receiving a command over a paging system utilizing a paging receiver (14). The message that is sent to the paging receiver (14) is encrypted. This encryption is performed by utilizing a first level of encryption wherein a message is generated including a secondary address, command information and a CRCC check byte. This is encrypted by utilizing an encryption table of randomly generated numbers at a central office location and then utilizing a corresponding encryption table at the receive location for the decryption operation. An index byte is utilized to determine the value selected from the encryption table at the central location which is forwarded to the receiver such that the same values are extracted from that encryption table. These values are assembled into a decryption key which is similar to the encryption key at the central office. Once decrypted, the command information must then be retrieved. The command information sent is in the form of randomly generated numbers that can be correlated with a command. This correlation is performed at the central office and then re-indexed to determine what the command was at the receiver. The CRCC check is then performed after inserting the actual command into the word.